206 ESSAYS. 
ranges. Through most of California these two Pacific forests 
are separate; in the northern part of that State they join, 
and form one rich woodland belt, skirting the Pacific, backed 
by the Cascade Mountains, and extending through British 
Columbia into our Alaskan territory. 
So we have two forest regions in North America, — an At- 
lantic and a Pacific. They may take these names, for they 
are dependent upon the oceans which they respectively bor- 
der. Also we have an intermediate isolated region or isolated 
lines of forest, flanked on both sides by bare and arid plains, 
— plains which on the eastern side may partly be called 
prairies, on the western, deserts. 
This mid-region mountain forest is intersected by a trans- 
verse belt of arid and alkaline plateau, or eastward of grassy 
plain — a hundred miles wide from north to south, — through 
which passes the Union Pacific Railroad. This divides the 
Rocky Mountain forest into a southern and a northern por- 
tion. The southern is completely isolated. The northern, in 
a cooler and less arid region, is larger, broader, more dif- 
fused. Trending westward, on and beyond the northern 
boundary of the United States, it approaches, and here and 
there unites with, the Pacific forest. Eastward, in northern 
British territory, it makes a narrow junction with northwest- 
ward prolongations of the broad Atlantic forest. 
So much for these forests as a whole, their position, their 
limits. Before we glance at their distinguishing features and 
component trees, I should here answer the question, why 
they occupy the positions they do;— why so curtailed and 
separated at the south, so much more diffused at the north, 
but still so strongly divided into eastern and western. Yet I 
must not consume time with the rudiments of physical geog- 
raphy and meteorology. It goes without saying that trees 
are nourished by moisture. They starve with dryness and 
they starve with cold. A tree is a sensitive thing. With its 
great spread of foliage, its vast amount of surface which it 
cannot diminish or change, except by losing that whereby it 
lives, it is completely and helplessly exposed to every atmos- 
pherie change; or at least its resources for adaptation are 
